The present disclosure relates to an organic electro luminescence (EL) display panel using organic EL elements utilizing electroluminescence of organic materials and a method of manufacturing an EL display panel using the same.
In recent years, as a display panel for use in a display apparatus such as a digital television set, an organic EL display panel in which a plurality of organic EL elements are arranged in a matrix pattern on a substrate has been put to practical use.
In an organic EL display panel, in general, a light emitting layer of each organic EL element and the adjacent organic EL element are partitioned from each other by an insulating layer formed from an insulating material. In an organic EL display panel for color display, organic EL elements form sub-pixels that emit light in RGB colors individually, and the RGB sub-pixels adjacent to one another are combined to form a unit pixel in color display.
The organic EL element has a basic structure in which a light emitting layer containing an organic light emitting material is disposed between a pair of electrodes. At the time of driving, a voltage is impressed between the pair of electrodes, and light is emitted attendant on recombination of holes and electrons injected into the light emitting layer.
An organic EL element of the top emission type has an element structure in which a pixel electrode, organic layers (inclusive of a light emitting layer), and a common electrode are sequentially provided over a substrate. Light from the light emitting layer is reflected by the pixel electrode formed from a light reflecting material, and is emitted upward from the common electrode formed from a light transmitting material.
The common electrode is often formed over the whole surface of the substrate. When the electric resistance of the common electrode is high, sufficient current supply is not attained, due to a voltage drop, and light emission efficiency is thereby lowered, at parts far from a current feeding part. This may lead to generation of variability in luminance.
In view of this problem, Japanese Patent Laid-open No. 2002-318556 proposes a technique of providing an auxiliary electrode for lowering the resistance of the common electrode. Specifically, Japanese Patent Laid-open No. 2002-318556 discloses a configuration in which an auxiliary electrode is formed in the same layer as a pixel electrode, and is electrically connected to the common electrode while being electrically insulated from the pixel electrode.